Bypassing the Stiffness Cliff: Biological Impedance Matching for Shoulder Arthroplasty in the Metaboli cally Compromised Host

Abstract Patients with chronic kidney disease–mineral and bone disorder (CKD-MBD) present a biomechanical paradox: a high-demand joint environment coupled with a metabolically compromised skeletal substrate. In this high-entropy host bed, rigid glenoid implants can create a pronounced impedance mismatch (stiffness cliff) at the implant-bone interface, amplifying interfacial stresses and predisposing to early loosening. We report a hemodialysis patient with end-stage renal osteodystrophy and advanced glenohumeral arthropathy with substantial glenoid bone loss. During hemi-shoulder arthroplasty, the resected humeral head was contoured as a structural autograft to resurface the glenoid and restore containment. This in-situ reconstruction repurposed the resected bone as a biological impedance matcher, avoiding the introduction of a rigid metal-bone interface. At final follow-up, active forward flexion 110°, abduction 90°, external rotation 25°, and internal rotation to L5 were achieved with pain relief, and radiographs showed maintained graft position without lucency. Autologous humeral-head glenoid resurfacing reframes glenoid reconstruction as a physics-informed biological coupling strategy designed to smooth stress transmission across a metabolically fragile interface.